Chemical availability of mercury in stream sediments from the Almaden area, Spain

cited By 37International audienceThe chemical speciation, fractionation and availability of mercury in sediments from a cinnabar mining area (Almaden, Spain) was studied with different extraction and analytical procedures, in order to determine the degree to which the ecosystem is harmed by this pollutant. Three total extraction procedures, a sequential extraction and the speciation of organo-mercury compounds were performed in nine sediment samples. In the study area, although concentrations of mercurycan be extremely high (up to 1000 mg kg-1), no organo-mercury compounds were detected (< 2 μg kg-1) and the availability of this element seems restricted. One of the methods for total extraction presented considerably lower recovery in Almaden's sediments, yet the results were controlled with certified reference materials. This disagreement was attributed to the fact that the mercury is in a refractory form. Sequential extraction was able to show that most of the mercury is associated with sulfides (probably as metacinnabar) or in the residual refractory phase (probably as red cinnabar)

Evaluation of host-guest complex formation between a benzimidazolic derivative and cyclodextrins by UV-VIS spectrophotometry and differential scanning calorimetry

Abstract Interactions between a benzimidazolic derivative, omeprazole (OME), beta-cyclodextrin (ßCD) and a chemically modified ßCD, methyl-beta-cyclodextrin (MßCD) were investigated in aqueous solution by UV-VIS spectroscopy and in solid state by differential scanning calorimetry (DSC). Phase solubility studies were used to evaluate the complexation in aqueous solution. The two solubility diagrams obtained were AL type, indicating the formation of a drug-cyclodextrin complex with 1:1 stoichiometry. The complex of OME with MßCD showed a higher stability constant (K S) than those with ßCD. Some evidences of inclusion complexation in solid state were obtained from DSC. Only in thermal curves of OME-ßCD lyophilized product and in OME-MßCD spray-dried and lyophilized systems the melting point of the drug disappeared completely suggesting the possible formation of an inclusion complex